The head of the United Nations warned of nuclear weapon threats, such as the possibility terrorists could obtain them, on Friday in Monterey.

Secretary-General Ban Ki-moon told a crowd of about 200 invitation-only guests at the Monterey Institute of International Studies that nuclear disarmament progress "is off track."

"Delay comes with a much higher price tag," he said. "The longer we delay, the greater the risk that these weapons will be used ... and even terrorists may acquire these nuclear bombs."

Ban, 68, said all nations with nuclear weapons need to make disarmament and arms control a priority.

"There are no right hands for wrong weapons," he said.

The secretary-general said nuclear-capable member states must come up with a "bold set of measures" to increase transparency of its nuclear arsenal.

Ban criticized President Barack Obama for not signing the Comprehensive Test-Ban Treaty, which bans all nuclear explosions by military and civilians.

"We were assured by President Obama when he was elected that the U.S. would ratify this CTBT," he said. "But somehow, it has not happened."

The treaty has been signed by 44 countries since it was introduced in 1994, the U.N.'s website says.

Ban also said U.N. member states should reduce the money they spend on military and use it for education, fighting global warming and other issues.

"The profits of the arms industry are built on the suffering of ordinary people," he said.

He said there were reasons for alarm in Iran and North Korea.

The U.N. chief said he visited Iran last August and was not convinced its nuclear program was peaceful. He also said North Korea's successful rocket launch in December "exacerbated global concern of its pursuit of nuclear weapons."

Ban said he supported Obama's proposal for stricter U.S. gun laws, despite saying it was a "domestic issue."

He said it is almost impossible to run into a private citizen in South Korea with a gun, "so there are many things that I cannot understand."

"I welcome President Obama's announcement," he said. "... I hope this will be helpful and I hope Congress will support his proposal."

Ban was the South Korean minister of foreign affairs for 37 years before coming to the U.N. He earned a master's degree in public administration at Harvard University, according to his official U.N. biography.

Disarmament, arms control and nonproliferation have been key issues for Ban since his appointment in 2007.

MIIS graduate student Aoi Sato, 27, of Japan, said she was in Hiroshima when Ban came in August 2010 to speak about the harm of nuclear weapons.

"I'm so impressed he hasn't changed," she said after the speech. "I'm impressed with him as a man and a leader."